Message-ID: <5289D0AE.20707@vmware.com>
Date: Mon, 18 Nov 2013 10:32:46 +0200
From: Heikki Linnakangas <hlinnakangas@vmware.com>
Organization: VMware
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CC: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>,
 Sergey Burladyan <eshkinkot@gmail.com>
Subject: Re:  freeze cannot be finished
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Committed, thanks for the report!

On 16.11.2013 22:05, Миша Тюрин wrote:
> Hello!
>
> Could anyone review patch suggested by Jeff Janes ?
>
> Initial thread http://www.postgresql.org/message-id/flat/1384356585.995240612%40f50.i.mail.ru
>
> Thanks in advance!
>
>>
>> On Wed, Nov 13, 2013 at 3:53 PM, Sergey Burladyan  < eshkinkot@gmail.com > wrote:
>>> Jeff Janes < jeff.janes@gmail.com > writes:
>>>
>>> If I not mistaken, looks like lazy_scan_heap() called from lazy_vacuum_rel()
>>> (see [1]) skip pages, even if it run with scan_all == true, lazy_scan_heap()
>>> does not increment scanned_pages if lazy_check_needs_freeze() return false, so
>>> if this occurred at wraparound vacuum it cannot update pg_class, because
>>> pg_class updated via this code:
>>>
>>>      new_frozen_xid = FreezeLimit;
>>>      if (vacrelstats->scanned_pages < vacrelstats->rel_pages)
>>>          new_frozen_xid = InvalidTransactionId;
>>>
>>>      vac_update_relstats(onerel,
>>>                          new_rel_pages,
>>>                          new_rel_tuples,
>>>                          new_rel_allvisible,
>>>                          vacrelstats->hasindex,
>>>                          new_frozen_xid);
>>>
>>> so i think in our prevent wraparound vacuum vacrelstats->scanned_pages always
>>> less than vacrelstats->rel_pages and pg_class relfrozenxid never updated.
>>
>> Yeah, I think that that is a bug.  If the clean-up lock is unavailable but the page is inspected without it and found not to need freezing, then the page needs to be counted as scanned, but is not so counted.
>>
>> commit bbb6e559c4ea0fb4c346beda76736451dc24eb4e
>> Date:   Mon Nov 7 21:39:40 2011 -0500
>>
>> But this was introduced in 9.2.0, so unless the OP didn't upgrade to 9.2 until recently, I don't know why it just started happening.
>>
>> It looks like a simple fix (to HEAD attached), but I don't know how to test it.
>>
>> Also, it seem like it might be worth issuing a warning if scan_all is true but all was not scanned.
>>
>> Cheers,
>>
>> Jeff
>>
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>>
>
> --
>
>
>
>


-- 
- Heikki


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